Audio Input Shield

(there’s an 8 pin header missing above)

Analog Envelope FollowerArduino sound amplitude detector

Envelope follower is a common term for analog modular synthesizer users, by definition it’s “used to detect the amplitude variations of an incoming signal to produce a control signal that resembles those variations.” meaning that it follows the audio amplitude envelope creating a voltage output that resembles the audio signal volume, in this case between 0 and +5 volts